Zero-pressure balloon catheter and method for using the catheter

ABSTRACT

A safety catheter includes a multi-lumen shaft. The shaft has a proximal shaft portion with a distal end having a given outer diameter and a distal tip portion having an outer diameter less than the given outer diameter. A hollow balloon is disposed at a junction of the proximal shaft portion and the distal tip portion. The balloon has a distal leg fixedly secured to the distal tip portion and a proximal leg removably secured to the proximal shaft portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application:

-   -   claims the benefit under 35 U.S.C. §119(e) of U.S. provisional        application No. 61/260,271 filed Nov. 11, 2009; and    -   is a continuation-in-part of U.S. patent application Ser. No.        11/339,258, filed Jan. 25, 2006 (which application claims the        benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent        Application Nos. 60/647,204 and 60/647,205, both filed Jan. 26,        2005),        the prior applications are hereby incorporated herein by        reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a catheter, especially a flexiblepressure-limiting or zero-pressure balloon catheter and a method forusing the catheter.

2. Description of Related Prior Art

A number of conventional balloon catheters exist in the prior art. Somecatheters are used to drain the bladder of a patient during surgicalprocedure or to treat bladder and/or urethra or prostate conditions, forexample. For example, a common balloon catheter made by RUSCH® andreferred to as a Foley catheter is widely used today for treating anddraining a patient's bladder. The Foley catheter is shown in FIG. 1 andhas a multi-lumen shaft 1 that is disposed in the urethra 10, a balloonportion 3 disposed at the distal end of the shaft 1, a fluid drainsection 4 disposed at the distal end of the balloon 3, and a curved,distal guiding tip 5 at the distal-most end of the entire catheter. Whenplaced properly, the proximal-most side of the inflated balloon 3 restson the interior wall 31 of the bladder 30, entirely blocking off theurethrovesical junction 11 connecting the bladder 30 and the urethra 10.In such a position, the fluid drain section 4 allows continuous drainageof the bladder 30 and the balloon 3 virtually entirely prevents thecatheter from slipping out of the bladder. This ideally insertedposition is shown in FIG. 1. As used herein, a fluid can be either aliquid or a gas. Exemplary fluids for inflating a balloon 3 are saline,air, or carbon dioxide gas. Exemplary fluids drained by the cathetersmentioned herein include urine and blood.

Basically, the catheter has tube-like body with two lumens passingtherethrough. The larger lumen 120 (see FIG. 2) is open to the bladder(distally) and empties into an ex-corporeal bag (proximally) foreventual disposal. A smaller lumen 130 is used to inflate the balloon 3with water (typically) using a syringe attached to the inflation lumenfitting 260. When inflated in the bladder, for example, the catheter isprevented from sliding out of the urethra in use.

Over 96 million indwelling catheters are sold worldwide on an annualbasis. Twenty four million catheters are sold to hospitals in the U.S.There are numerous complications associated with those catheters thatneed to be prevented. These complications are responsible for increasesin hospital stays, excessive bleeding, mortality, as well as morbidity.They also cause an increased expense and burden on the already-stressedhealth care system.

The complications result from several different mechanisms. First, andprobably most common, is improper placement of the catheter. Because ofthe unique anatomy of the male urethra, placing a urethral catheter forurinary drainage can be difficult. A problem arises when the physician,technician, or nurse thinks that the catheter is actually in a properposition when it is not. The proper position for the catheter is withthe balloon located in the cavity of the bladder. In this position, thetip distal to the balloon is located in the bladder and is used to drainthe bladder cavity.

For placement of this catheter in the bladder 30 in the ideal position,however, the physician or technician has no visual aid. As shown in FIG.1, the wall 40 defining the urethrovesical junction 11 is very short inthe longitudinal direction of the urethra 10. If the physician insertsthe catheter too far into the bladder 30, no damage occurs from ballooninflation; however, there is a possibility of leakage around the balloon3, which, under normal conditions, helps to lubricate the urethra 10. Insuch a case, gentle proximal movement will move the proximal side of theballoon 3 against the urethrovesical junction 11. The bladder 30 canthen easily expand and stretch to compensate for the balloon 3. A normalbladder capacity is 400 to 500 cc. A normal balloon capacity isapproximately 10 to 12 cc although larger balloons are sometimes used. Atypical balloon is 5 cc, however, most clinicians put 10 cc of water inthe balloon to inflate it. With 5 cc of water in the balloon, thediameter is approximately 2 cm and, with 10 cc, the diameter isapproximately 2.5 cm.

The complication occurs when the technician and/or nurse inflates theballoon when the balloon is not in the bladder. If the technician doesnot insert the catheter in far enough, then the balloon 3 will beinflated within the urethra 10—a condition that is common and, not onlyis it to be avoided at all costs, is a frequent cause of bladderinfections created during a hospital or clinic visit. Infections arisebecause inflation of the bladder 3 inside the urethra 10 causes theurethra 10 to stretch too far and tear. Even though the urethra 10 is aflexible tube, it has limits to which it can be safely stretched fromwithin. Almost every balloon catheter has a balloon outerdiameter/circumference that well-exceeds the safe stretching limit ofthe urethra 10. Therefore, if the balloon catheter is not inserted farenough, inflation of the balloon 3 will cause serious injury to theurethra 10. This is especially true with elderly patients who haveurethra 10 that are not as elastic as younger patients. Also, just asimportant is the change in anatomy of older males, in particular, theprostatic portion of the urethra. With age, the prostate becomes largerand, sometimes, the catheter cannot be advanced through the prostaticportion of the urethra. When this occurs, the technician does not insertthe catheter all the way into the bladder and inflates the balloonwithin the urethra, causing severe bleeding and damage.

The elastomeric balloon of present-day catheter products requiresrelatively high pressures to initiate inflation and expand to anexpected full-diameter shape upon over-inflation. As such, whenincorrectly placed in the urethra, the rapid inflation, combined withthe high-pressure, causes the balloon to tear the surrounding membrane,called the mucosa. Tearing of the urethra 10 in this way causes bleedingand allows bacteria to enter into the bloodstream at the tear site, thuscausing the subsequent bladder infection. Significant bleeding canbecome life threatening. The urethra can normally dilate severalmillimeters; however, when the balloon is inflated, this dilation isusually several centimeters. Also, without sufficient and immediateventing of the balloon inflation fluid after placement, an accidental orintentional pull on the catheter externally can and does cause extensivebodily harm to a patient fitted with the device.

Life threatening bleeds, especially in patients who are anticoagulated,can and do occur. Also when the urine is infected, as inimmunocompromised patients and the elderly, the bacteria enter the bloodstream and can cause serious infections (e.g., sepsis), which frequentlycan lead to death. If the patient survives the initial trauma, thenlong-term complications, such as strictures, can and usually do occur.Strictures are narrowings within the urine channel and usually requireadditional procedures and surgeries to correct.

Other mechanisms of catheter-induced injuries are inadvertentmanipulation of the tubing or dislodging of the balloon—caused when thecatheter is pulled from outside the patient due to a sudden jerk ortension. This commonly happens when the patient is ambulating ortraveling from the bed to the commode or bathroom. The tubing mayinadvertently become fixed while the patient is still moving, at whichtime a sudden jerk is imparted upon the balloon and pulls the ballooninto the urethra to tear it, causing severe pain and bleeding. Injurycaused by the improper, inadvertent, and/or early removal of an inflatedballoon catheter is referred to as iatrogenic injury (also referred toas an in-hospital injury). Hundreds of thousands of such iatrogenicinjuries occur each year—all of which need to be prevented, not only forpatient safety, but also because the cost imposed on the medical healthindustry for each injury is enormous.

Yet another scenario occurs when the patient deliberately pulls on thecatheter, thereby causing self-induced pain and injury to the urethra.This commonly happens in confused patients, for example, patients innursing homes who have a disease or cognitive dysfunction problem, suchas Alzheimer's disease, or other diseases that make the patient unableto understand the necessity of having a catheter. Confusion occurs whenthe patient has a spasm causing a strong urge to urinate and pain.During the spasm, the confused patient often tugs and pulls on acatheter, which results in injury. Like iatrogenic injuries, theseself-induced injuries must be prevented.

The injuries mentioned herein are not limited to males and also causesevere damage to the female bladder and urethra. The injuries can alsooccur post-surgically, which makes the damage even more severe. Onecommon situation where injury is caused is when the patient is medicatedwith morphine or other analgesics that render the patient confused andunable to make rational decisions. Feeling the foreign body inside theurethra, the confused patient does not know to leave it alone and,instead, gives it the injury-causing tug. These injuries have beenwell-documented and are not limited to adults. Numerous injuries aredocumented in pediatric patients.

Usually, it takes time to make a diagnosis of patient-caused catheterinjury. Immediately after diagnosing the injury, a technician needs todeflate the catheter. However, once the urethra is torn, replacing thedamaged catheter with another catheter is quite difficult and, in fact,exacerbates the injury. Sometimes, the patient has to be taken to theoperating room to replace a urinary drainage tube once the injuryoccurs. Because catheters and leg bags are now used routinely in certainsituations during home health care, this scenario is not limited tohospitals and occurs at nursing homes and patients' homes.

Most of the recent catheter technology has been focused on reducingurinary tract infections that are caused by catheters, injuries that areusually the most common catheter-related complications.

In a conventional balloon 3, the balloon 3 has a substantially constantballoon wall thickness. The balloon 3 is fixed to the outer surface of afluid drainage line (not illustrated in FIG. 1) and is not intended tobe removed therefrom or to burst thereon unless an extraordinary amountof inflation occurs. If such an event happens, the material of theballoon will open at a random location based upon the microscopicfractures or weaknesses in the material itself. Such a tearing event isnot supposed to occur under any circumstances during use with a patient.

Prior art catheters are not constructed to prevent tearing of theurethra during a catheter implanting procedure and are not constructedto break in any predefined way. Accordingly, it would be beneficial toprovide a balloon catheter that does not inflate past the tearing limitof a urethra and deflates in a desired, predefined way under certainconditions.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a verylow or zero-inflation pressure balloon catheter and method for using thecatheter that overcome the hereinafore-mentioned disadvantages of theheretofore-known devices and methods of this general type and that doesnot inflate when the catheter is placed, for example, in the urethra,and quickly and rapidly deflates if pulled out prior to manual deflationof the balloon.

With the foregoing and other objects in view, there is provided, inaccordance with the invention, a safety catheter having a multi-lumenshaft having a proximal shaft portion having a distal end with givenouter diameter, a distal tip portion having an outer diameter less thanthe given outer diameter, and a hollow balloon disposed at a junction ofthe proximal shaft portion and the distal tip portion. The balloon has adistal leg fixedly secured to the distal tip portion and a proximal legremovably secured to the proximal shaft portion.

In accordance with another feature of the invention, at least theproximal leg of the hollow balloon is relatively inflexible and at leastthe distal end of the proximal shaft portion is relatively flexible, thedistal end of the proximal shaft portion and the proximal leg of thehollow balloon form a removable compression seal therebetween.

In accordance with a further feature of the invention, the removablecompression seal has a breakaway point at a pull force of betweenapproximately 1 pound and approximately 15 pounds applied to theproximal shaft portion.

In accordance with an added feature of the invention, the removablecompression seal has a breakaway point at a pull force of betweenapproximately 1 pound and approximately 5 pounds applied to the proximalshaft portion.

In accordance with an additional feature of the invention, the removablecompression seal has a breakaway point at a pull force of betweenapproximately 1.5 pounds and approximately 2 pounds applied to theproximal shaft portion.

In accordance with yet another feature of the invention, when theballoon portion is inflated with a fluid and a pull force of greaterthan approximately 15 pounds is applied to the proximal shaft portion,the compression seal exceeds a breakaway point and thereby deflates theinflated hollow balloon.

In accordance with yet a further feature of the invention, when theballoon portion is inflated with a fluid and a pull force of greaterthan approximately 5 pounds is applied to the proximal shaft portion,the compression seal exceeds a breakaway point and thereby deflates theinflated hollow balloon.

In accordance with yet an added feature of the invention, when theballoon portion is inflated with a fluid and a pull force of greaterthan approximately 2 pounds is applied to the proximal shaft portion,the compression seal exceeds a breakaway point and thereby deflates theinflated hollow balloon.

In accordance with yet an additional feature of the invention, theproximal leg is removably secured to the proximal shaft portion in aninverted orientation.

In accordance with again another feature of the invention, the hollowballoon is operable to fold back upon itself when removed from theproximal shaft portion.

In accordance with again a further feature of the invention, the hollowballoon is operable to inflate with and withstand pressures of betweenapproximately 0.2 atmospheres and 0.5 atmospheres without an appreciableincrease in diameter.

In accordance with again an added feature of the invention, the hollowballoon defines a balloon interior. The multi-lumen shaft has a proximalend, a fluid drain lumen defining a distal fluid drain opening at thedistal tip portion distally of the distal leg, and a proximal fluiddrain opening fluidically connected to the distal fluid drain opening.The shaft has balloon inflation lumen fluidly connected to the ballooninterior adjacent the proximal end of the multi-lumen shaft and aninternal balloon valve operable to selectively open a channel betweenthe fluid drain lumen and the balloon interior.

In accordance with a concomitant feature of the invention, the internalballoon valve is operable to open the channel when a pressure in theballoon is between approximately 0.3 atmospheres and approximately 1.5atmospheres.

The zero-pressure balloon catheter of the present invention preventsinjury by having the balloon automatically deflate before an injury canoccur, for example, when being forced to withdraw from the bladder orbeing forced to inflate within a urethra. While the catheter of thepresent invention makes it a safer device for urinary drainage, thepresent invention can also be used for any procedures in which balloonsare used to occlude cavities. Examples of these procedures includecoronary artery vessels and peripheral vascular vessels, such as theaorta and extremity vessels. Balloon dilations of other lumens, such asureters and the esophagus, are also candidates for use of the catheterof the present invention.

Some of the embodiments of the present invention utilize a valve (e.g.,a slit valve) that permits reuse when utilized. With embodiments havingno such valve, the invention is a single use after deflation occurs.Although deflation of such a catheter renders it useless, the act ofimmediate deflation protects the patient from serious harm and cost ofreplacing a catheter is minimal as compared to the cost of treatingcatheter-induced injury. Prevention of such injuries is becoming moreand more important because the injuries are commonplace. The increaseoccurs for a number of reasons. First, a greater percentage of thepopulation is aging. Second, there is a current trend to useless-skilled health care personnel to perform more procedures and to beresponsible for treatment, both of which save money. The shortage ofnursing professionals (R.N.s) exacerbates this trend. The presenttendency is to use nursing professionals for more functions, such asadministration and delivery of medications. This leaves only theless-skilled technicians with the task of taking vital signs andinserting catheters. Under such circumstances, more injuries are likely.Lastly, catheter-related complications are becoming more severe due tothe increased use of anticoagulation medication, such as PLAVIX®, thatis frequently prescribed in treating cardiovascular disease.

Yet another possible complication arising from the standard Foleycatheter is that the balloon will not deflate even when the deflationmechanism is activated. This situation can occur, for example, becausethe wrong fluid is used to inflate the balloon or when a fluid, such assaline, crystallizes, which happens occasionally. Sometimes, the abilityto deflate the catheter is interrupted because the drainage channel thatis used to deflate the balloon becomes obstructed, which is common ifthe catheter is left in place too long. Remedy of such a scenarioinvolves an invasive procedure, which includes threading a needle orother sharp object somewhere through the body cavity to puncture theballoon and, thus, dislodge the catheter. Yet another possiblecomplication can occur when there is a stricture evolved. A stricture isscar tissue in the urethra that impedes the passage of the catheter. Insuch a case, the technician sometimes uses excessive force in trying topush the catheter into the bladder, thereby causing a tear and bleeding.

With the zero-pressure auto-deflating balloon of the present invention,the technician, nurse, or doctor merely needs to pull on the catheter tocause the catheter to automatically deflate, thus sparing the patientfrom any additional surgical procedures.

The added benefit of the present invention is not just for safety,significant financial benefits arise as well. It is believed thatcatheter-induced injuries are much more common than public documentationsuggests. Catheter-related trauma occurs roughly at least once a week ina large metropolitan hospital. Usually, each incident not only increasesthe patient's hospital stay substantially, but also the expense of thestay. Each incident (which is usually not reimbursed by insurance) canincrease the cost to the hospital by thousands, even tens of thousands,of dollars.

When additional surgery is required to repair the catheter-inducedinjury, increased expense to the hospital is not only substantial, iflitigation occurs as a result of the injury, damages awarded to thepatient can run into the millions of dollars. The catheter of thepresent invention, therefore, provides a safer catheter that has thepossibility of saving the medical industry billions of dollars.

To prevent urethra tearing occurrences due to premature-improperinflation of the balloon and/or due to premature removal of an inflatedballoon, an exemplary embodiment of the invention of the instantapplication provides a balloon safety valve.

The maximum stress that a typical urethra can take without tearingand/or breaking is known and is referred to as a maximum urethrapressure. It is also possible to calculate how much pressure is exertedupon the exterior of a balloon of a balloon catheter by measuring thepressure required to inflate the balloon. Knowing these two values, itis possible to construct a balloon that breaks rapidly and/or ceasesinflation if the maximum urethra pressure is exceeded.

For example, in a first exemplary embodiment, the balloon, which istypically some kind of rubber, silicone, or plastic, can be made with abreaking point that instantly deflates the balloon if the pressure inthe balloon exceeds the maximum urethra pressure. It is acknowledged andaccepted that, once the balloon breaks, this catheter is useless andmust be discarded because the cost of patient injury far outweighs thecost of the disposable catheter. Also, such a balloon is limited toinflation with a bio-safe fluid to prevent unwanted air/gas fromentering the patient. If, however, air or other gas will not injure thepatient, the fluid can be air or another gas.

As an alternative to a one-use breaking safety valve, a multi-usepressure valve can be added to the balloon inflation lumen and can beset to open into the drainage lumen if the maximum urethra pressureexceeded in the balloon or the balloon inflation lumen. Such a valve canbe located near or at the balloon inflation port. Any combination of theabove embodiments is envisioned as well.

Another exemplary embodiment of the present invention provides thecatheter with a balloon that inflates with virtually no pressure. Asused herein, “virtually no pressure,” “zero-pressure” and “low-pressure”are used interchangeably and are defined as a range of pressure betweenapproximately standard atmospheric pressure and 0.3 atmospheres (5psig). This is in contrast to “high-pressure,” which is greater thanapproximately 1.5 atmospheres (22 psig). With such a configuration, thezero-pressure balloon can be deflated with virtually no force. As such,when the clinician attempts to inflate the zero-pressure balloon of thepresent invention within a urethra, the balloon simply does not inflate.Likewise, when the already inflated balloon within the bladder is forcedinto the urethra, such deflation needs virtually no pressure to collapsethe balloon to fit into the urethra. In both circumstances, injury tothe urethra is entirely prevented.

Although the invention is illustrated and described herein as embodiedin a zero-pressure balloon catheter and a method for using the catheter,it is, nevertheless, not intended to be limited to the details shownbecause various modifications and structural changes may be made thereinwithout departing from the spirit of the invention and within the scopeand range of equivalents of the claims. Additionally, well-knownelements of exemplary embodiments of the invention will not be describedin detail or will be omitted so as not to obscure the relevant detailsof the invention.

Other features that are considered as characteristic for the inventionare set forth in the appended claims. As required, detailed embodimentsof the present invention are disclosed herein; however, it is to beunderstood that the disclosed embodiments are merely exemplary of theinvention, which can be embodied in various forms. Therefore, specificstructural and functional details disclosed herein are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one of ordinary skill in the art tovariously employ the present invention in virtually any appropriatelydetailed structure. Further, the terms and phrases used herein are notintended to be limiting; but rather, to provide an understandabledescription of the invention. While the specification concludes withclaims defining the features of the invention that are regarded asnovel, it is believed that the invention will be better understood froma consideration of the following description in conjunction with thedrawing figures, in which like reference numerals are carried forward.The figures of the drawings are not drawn to scale.

Before the present invention is disclosed and described, it is to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting. The terms “a” or “an”, as used herein, are defined as one ormore than one. The term “plurality,” as used herein, is defined as twoor more than two. The term “another,” as used herein, is defined as atleast a second or more. The terms “including” and/or “having,” as usedherein, are defined as comprising (i.e., open language). The term“coupled,” as used herein, is defined as connected, although notnecessarily directly, and not necessarily mechanically.

As used herein, the term “about” or “approximately” applies to allnumeric values, whether or not explicitly indicated. These termsgenerally refer to a range of numbers that one of skill in the art wouldconsider equivalent to the recited values (i.e., having the samefunction or result). In many instances these terms may include numbersthat are rounded to the nearest significant figure. In this document,the term “longitudinal” should be understood to mean in a directioncorresponding to an elongated direction of the catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail byexemplary embodiments and the corresponding figures. By schematicillustrations that are not true to scale, the figures show differentexemplary embodiments of the invention.

FIG. 1 is a longitudinally diagrammatic cross-sectional view of a priorart catheter ideally placed in a urethra and a bladder of a malepatient;

FIG. 2 is a fragmentary, enlarged, cross-sectional view of a distalportion of a first embodiment of a pressure-limiting balloon catheteraccording to the invention;

FIG. 3 is a fragmentary, enlarged cross-sectional view of a proximalportion of a second embodiment of a pressure-limiting balloon catheteraccording to the invention;

FIG. 4 is a fragmentary, enlarged, cross-sectional view of a firstalternative configuration of the safety valve of FIG. 3;

FIG. 5 is a fragmentary, enlarged, cross-sectional view of a secondalternative configuration of the safety valve of FIG. 3;

FIG. 6 is a fragmentary, enlarged, cross-sectional view of a thirdalternative configuration of the safety valve of FIG. 3;

FIG. 7 is a fragmentary, further enlarged, cross-sectional view of thesafety valve of FIG. 6;

FIG. 8 is a fragmentary, further enlarged, cross-sectional view of afourth alternative configuration of the safety valve of FIG. 3;

FIG. 9 is a fragmentary, partially hidden, perspective view of anexemplary embodiment of a zero-pressure safety catheter according to theinvention;

FIG. 10 is a cross-sectional view of a portion of the catheter of FIG. 9at section line 10-10;

FIG. 11 is a process flow diagram of a method of forming a zero-pressureballoon according to the invention;

FIG. 12 is a process flow diagram of a method of attaching azero-pressure balloon according to the invention;

FIG. 13 is a fragmentary, enlarged, perspective view of a distal portionof an exemplary embodiment of a zero-pressure catheter according to theinvention;

FIG. 14 is a cross-sectional view of a slit-valve portion of thecatheter of FIG. 13 at section line 14-14;

FIG. 15 is a cross-sectional view of an alternative embodiment of aslit-valve portion of the catheter of FIG. 13 at section line 15-15;

FIG. 16 is a fragmentary, enlarged, partially cross-sectional view of aneverting catheter according to the invention in a correctly insertedposition in the bladder;

FIG. 17 is a fragmentary, enlarged, partially cross-sectional view ofthe catheter of FIG. 16 being pulled distally out of the bladder andbeginning its everting deflation; and

FIG. 18 is a fragmentary, enlarged, partially cross-sectional view ofthe catheter of FIG. 16 with the everting deflation complete.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

While the specification concludes with claims defining the features ofthe invention that are regarded as novel, it is believed that theinvention will be better understood from a consideration of thefollowing description in conjunction with the drawing figures, in whichlike reference numerals are carried forward.

Herein various embodiment of the present invention are described. Inmany of the different embodiments, features are similar. Therefore, toavoid redundancy, repetitive description of these similar features maynot be made in some circumstances. It shall be understood, however, thatdescription of a first-appearing feature applies to the later describedsimilar feature and each respective description, therefore, is to beincorporated therein without such repetition.

Referring now to the figures of the drawings in detail and first,particularly to FIG. 2 thereof, there is shown a first embodiment of apressure-limiting balloon catheter 100 that does not inflate past thetearing limit of a lumen in which the catheter 100 is placed, forexample, in the urethra.

To prevent occurrences of urethra tearing due to premature-improperinflation of the balloon and/or due to premature removal of an inflatedballoon, the invention of the instant application provides the balloon110 with a balloon safety valve 112. As set forth above, in a balloon 3of a conventional catheter (see reference numerals 1 to 5 in FIG. 1),the high-pressure balloon 3 is fixed to the outer surface of the fluiddrainage lumen 120 (not shown in FIG. 1) and is not intended to beremoved therefrom or to burst thereon unless an extraordinary amount ofinflation occurs. Such a tearing event is not supposed to occur underany circumstances during use with a patient. If such an event happens,the material of the balloon 3 will open at a random location, based uponthe microscopic fractures or weaknesses in the material itself, and riskof serious damage to the patient is associated with the bursting, aswell as a risk of balloon fragmentation, which could leave pieces of theballoon 3 inside the patient after removal of the catheter 1.

In contrast to such conventional devices, the balloon 110 of the presentinvention is created specifically to tear when a predefined pressureexists in or is exerted on the balloon 110. The controlled tear willoccur because the balloon safety valve 112 is present. Conventionalballoons have constant balloon wall thicknesses (before inflation). Incontrast thereto, the balloon safety valve 112 in the first embodimentis a defined reduction in balloon wall thickness. This reduction createsa breaking point or selected breaking points at which the balloon 110 isintended specifically to break when a predefined force exists in or isimparted on the balloon 110. Because the balloon 110 is made of amaterial having a known tearing constant—dependent upon the thicknessthereof (which is determined experimentally for different thicknesses ofa given material prior to use in a patient), the balloon safety valve112 of the present invention for urethra applications is matched tobreak when the pressure inside or exerted on the balloon 110 approachesthe maximum urethra pressure.

In the embodiment shown in FIG. 2, a decreased thickness is formed as afirst semi-circumferential groove 114 near a proximal end of the balloon110 and/or as a second semi-circumferential groove 116 near a distal endof the balloon 110. The grooves 114, 116 can have any cross-sectionalshape, including, trapezoidal, triangular, square, or rectangle, forexample. Because rubber, plastic, and silicone materials tear well withthinner cuts, a relatively triangular shape or one with a narrow bottomcan be an exemplary configuration. To make sure that the entire balloon110 of the illustrated embodiment does not completely tear away from thefluid drainage lumen 120, both grooves 114, 116 do not extend around theentire circumference of the balloon 110. As shown to the left of theproximal groove 116 in FIG. 2, the groove 116 is not present on at leastan arc portion 118 of the circumference of the balloon 110. The arcportion is defined to be sufficiently large so that, when the catheter100 is removed from the patient, the balloon 110 cannot tear awayentirely from the catheter 100 (and create the disadvantageousfragmentation situation as set forth above). The illustrated balloonsafety valve 112 is, therefore, fashioned to keep the balloon 110 in onepiece after breaking and remain firmly connected to the catheter 100 toinsure that no piece of the balloon 110 will be left inside the patientafter actuation of the balloon safety valve 112.

It is noted that the balloon 110 is inflated through an inflation lumen130 having a proximal opening, typically formed by a female end of aluer connector (see 260 in FIG. 3). The female end is connected to anon-illustrated inflation device, for example, a distal end of a syringefor inflation of the balloon 110.

In this first embodiment, the balloon can be of rubber, silicone, orplastic, for example. Once the balloon breaks, the catheter is uselessand must be discarded. Because the balloon 110 in this embodiment willbreak inside the patient, it should be inflated with a bio-safe fluid toprevent unwanted air, gas, or bio-unsafe fluid from entering thepatient. In certain circumstances where balloon catheters are used, airor gas will not injure the patient if let out into the patient's bodycavity. In such circumstances, the inflating fluid can be air underpressure, for example.

Maximum urethra pressure can also be tailored to the individual patient.Based upon a urethral pressure-measuring device, the patient's maximumurethra pressure can be measured before the catheter 100 is placedtherein. A set of catheters 100 having different safety valve breakingconstants can be available to the physician and, after estimating orcalculating or knowing the patient's maximum urethra pressure, thephysician can select the catheter 100 having a safety valve breakingconstant slightly or substantially smaller than the patient's maximumurethra pressure. Accordingly, if the pressure in the balloon 110approaches the patient's maximum urethra pressure for any reason,whether it is due to over-inflation, improper placement, and/orpremature removal, the balloon 110 is guaranteed to break prior to thepatient's lumen, in particular, the patient's urethra, prior to causingiatrogenic injury.

A second embodiment of the one-use breaking safety valve of apressure-limiting balloon catheter 200 is shown in FIG. 3. The catheter200 has a fluid drainage lumen 220, a balloon inflation lumen 230, and asecondary lumen 240.

The fluid drainage lumen 220 is connected fluidically to the body cavity(i.e., the bladder 30) for draining fluid from the body cavity.

The secondary lumen 240 can be used for any purpose, for example, forhousing the radiation line that will supply energy to the radiation coil2. It can also be used for injecting fluid into any distal part of thecatheter 200 or even the body cavity itself.

The balloon inflation lumen 230 begins at a proximal end with aninflating connector 260 that, in an exemplary embodiment, is a femaleluer connector (of course, it can be a male luer connector too). Theballoon inflation lumen 230 continues through the body of the catheter200 all the way to the balloon 110 and is fluidically connected to theinterior of the balloon 110.

Alternatively or additionally, the balloon safety valve is fluidicallyconnected to the balloon inflation lumen 230. In a second embodiment ofthe safety valve 212, the valve 212 is formed integrally with theballoon inflation lumen 230 and is set to open into the environment(instead of into the patient) if the maximum urethra pressure isexceeded in the balloon 110 or the balloon inflation lumen 230. Becausethis safety valve 212 is located near or at the balloon inflation port260 in this configuration, fluid used to inflate the balloon will notenter the patient when the valve 212 opens.

The safety valve 212 in the second embodiment can merely be a narrowingof the distance between the balloon inflation lumen 230 and the outersurface 250 of the catheter 220. In FIG. 3, the valve 212 has arectangular cross-section and extends away from the balloon inflationlumen 230. As shown in FIGS. 4, 5, and 6, respectively, thecross-section can be triangular (peaked or pyramidical inthree-dimensions), curved (circular or cylindrical in three-dimensions),or trapezoidal (frusto-conical or bar-shaped in three-dimensions). Thecross-sections are shown in FIGS. 3 to 7 with the narrowing emanatingfrom the balloon inflation lumen 230 outward. As an alternative, thenarrowing can begin on the outer surface of the catheter and extendinwards towards the balloon inflation lumen 230. A further alternativecan have the narrowing extend from both the lumen 230 and the outersurface of the catheter.

The cross-sections illustrated are merely exemplary. What is importantis that the thickness t between the bottom 213 of the valve 212 and theouter surface 250 of the catheter 220 in comparison to the thickness Tof the catheter body over the remainder of the balloon inflation lumen230. An enlarged view of this thickness comparison is illustrated inFIG. 7. As long as the thickness t is smaller than the thickness T(t<T), and as long as the force F_(b) required to break the balloon isgreater than the force F_(sv) required to break the portion 213 of thesafety valve 212 (F_(b)>F_(sv)), then the portion 213 of the safetyvalve 212 is virtually guaranteed to break every time pressure exertinga force F in the balloon inflation lumen 230 is greater than the forceF_(sv) required to break the safety valve (F_(sv)>F).

Based upon this analysis, the force F_(sv) required to break the safetyvalve can be tuned to whatever a patient needs or a physician desiresand different sized valves can be available for any procedure andprovided in the form of a kit. Whether a standard maximum urethrapressure is used or a patient-specific maximum urethra pressure ismeasured and used, experiments can be conducted prior to use on apatient on various catheter thicknesses t to determine the pressureneeded to break the portion 213 of the safety valve 212. For example,ten different maximum urethra pressures can be known as desirablesetpoints and the thicknesses t can be varied such that pressurerequired to break the ten thicknesses correspond to the ten setpointpressures. If, then, ten catheters are placed in such a kit, each havingone of the ten thicknesses, then the physician has a range of 10 maximumurethra pressure values to use with the patient.

The safety valve 212 of the second embodiment need not be confined tothe body of the catheter 200. Instead, the inflating connector 260 can,itself, be equipped with the pressure relief valve 212. Alternatively, anon-illustrated modular attachment containing the safety valve 212 canbe attached to the inflating connector 260. Such a modular valveattachment is removable and replaceable (such as through a conventionalluer or even a screw-threaded connection). Accordingly, as long as thecatheter 200 can still be used after the valve 212 actuates (breaks),the used modular valve attachment can be replaced with a new attachment.The converse is also true for reuse of the attachment if the catheter200 breaks and the valve of the attachment remains unbroken. Adownstream end of the modular valve attachment (shaped as a luerconnector) is attached removably to an upstream end of the inflatingconnector 260 and the upstream end of the modular valve attachment is tobe connected to the balloon inflation device, which is commonly asyringe. The upstream end of the modular valve attachment is, likewise,a luer connector for easy connection to standard medical devices. Insuch a configuration, the safety valve 212, 312 of the present inventioncan be entirely separate from the catheter 200, 300 and, therefore, forma retrofitting device for attachment to any luer connector present onconventional catheters.

As an alternative to the one-use breaking safety valve of the secondembodiment, a multi-use pressure valve can be used. This thirdembodiment of the pressure-limiting balloon catheter 300 is illustratedin FIG. 8. The catheter 300 can be the same as the catheter 200 in FIG.3 except for the portion illustrated in FIG. 8. Instead of having anarrowing thickness t of the lumen wall, the valve portion 313 extendsentirely to the environment. However, a one-way valve 314 (shown onlydiagrammatically in FIG. 8) is attached to the open end of the valveportion 313 and is secured to the outer surface 250 of the catheter 300to close off the open end of the valve portion 313. The one-way valve314 can be secured directly to the outer surface 250 (e.g., with anadhesive) or a connector 315 (e.g., a threaded cap) can secure theone-way valve 314 to the open end of the valve portion 313. Regardlessof the configuration, the one-way valve 314 includes a device that doesnot permit fluid from exiting the lumen 230 until a given resistance Ris overcome. This given resistance R can be selectable by the physiciandepending upon the one-way valve that is chosen for use if a set ofone-way valves having different resistances R are available for use bythe physician. Just like the second embodiment, the resistance R can beset to correspond to desired maximum urethra pressure values. Therefore,when used, the fluid exits the one-way valve 314 into the environmentwell before the patient's maximum urethra pressure is exceeded by theballoon.

The one-way valve 314 can be a mechanical one-way valve. Additionally,the one-way valve 314 can be a material having a tear strengthcorresponding to the desired set of resistances R. The material can be afluid-tight fabric, a rubber, a plastic, or silicone different from thematerial making up the catheter. The material can even be a rubber,plastic, or silicone the same as the material making up the catheter buthaving a reduced thickness t than the thickness T of the catheter.Alternatively, the one-way valve 314 can be a slit valve. Variousexemplary embodiments of such a valve can be found in U.S. Pat. No.4,995,863 to Nichols et al., which is hereby incorporated herein byreference in its entirety.

Because the safety valve 212, 312 is located at the proximal end of thecatheter 200, 300, the distal end of the catheter 200, 300 can take theform of a distal end of a conventional balloon catheter 2, 3, 4, 5.Alternatively, the distal end shown in FIG. 2 can also be used forredundant over-pressure protection.

In another exemplary embodiment of the present invention, FIGS. 9 to 18illustrate alternatives to the elastomeric balloon described above. Inparticular, the above elastomeric balloon is replaced by a thin walled,pre-formed, fixed diameter balloon 1010 that inflates with virtually nopressure and withstands pressures between approximately 0.2 atmospheres(2.9 psi) and 0.5 atmospheres (7.35 psi), the latter of which isapproximately equal to the maximum urethra pressure, without anappreciable increase in diameter. Examples of such balloon materials andthicknesses are used in the medical field already, such as those used inangioplasty. Other exemplary materials can be those used in commercial(party) balloons, for example, MYLAR®, or similar materials such asnylon, PTA, PTFE, polyethylene and polyurethane, for example. In FIGS.10 and 12, the balloon 1010 is shown in a spherical shape. However, theballoon 1010 can be, for example, cylindrical with flat or conicallytapering ends.

The inflation balloon 1010 can be formed by heating a tubular materialwithin a mold or formed by heat-sealing thin sheets to one another(e.g., party balloons have two sheets). One example of the relativelynon-compliant, thin-walled balloon 1010 of the present invention isformed using a blow-molding process. In the blow-molding process, athermoplastic material such as nylon, polyurethane, or polycarbonate isextruded or formed into a hollow, tube-like shape (parison) and issubsequently heated and pressurized, usually with air, inside a hollowmold having a shape to form the final outer dimensions of the balloon.An example of the blow molded product is the common plastic soda orwater bottle containers.

One exemplary, but not limiting, process to form the zero-pressureballoon of the present invention is described with respect to FIG. 11and includes, in Step 1110, cutting a relatively short piece of“parison” tubing that is formed using standard “air-mandrel” extrusiontechniques. In Step 1120, one end of the tubing is sealed. The centerportion of the tubing is placed in a hollow mold, leaving both endsextending outside of the mold, in Step 1130. The center of the tubing isheated in Step 1140 with a hot stream of air through a small hole in thecenter of the mold for a few seconds to soften the tubing walls withinthe mold. The inside of the tubing is pressurized with air in Step 1150to stretch the tubing walls to conform with the inside dimensions of themold. After a short cooling period, an additional stretch of the formedballoon is done in Step 1160 by pulling on the (external) parison and,after a second “blowing” in the same mold in Step 1170, is used tocreate a very thin-walled balloon (much less than 0.001 inches,typically, based upon the parison wall thickness and the final balloondiameter). The extra (unblown) parison tubing is then cut off from bothends in Step 1180, leaving the thin walled, relatively supple balloonand its “legs” to be mounted to the catheter as described below.

This exemplary process can be used to create thin, non-compliantballoons for “angioplasty” of blood vessels at pressures exceeding 12atmospheres of pressure, for example. Although these pressures are notnecessary in the present application, it is witness to the fact thatvery strong thin-walled balloons can result from the above manufacturingprocess.

The present invention's thin, non-compliant zero-pressure balloon can beattached to the drainage catheter in a number of ways. In a firstexemplary attachment embodiment, reference is made to FIGS. 12, 13, and16. Each of the balloon's distal and proximal legs is attached to thedistal end of the drainage catheter using standard (FDA-approved)cements. The non-compliant, thin-walled balloon is dimensioned toenvelop the “slit valves” shown, for example, in FIG. 13, as anexemplary configuration of the invention. The balloon's thin walls allowfolding of the balloon without a significant increase in the catheterouter diameter for ease in catheter insertion.

A second exemplary, but not limiting, process to attach thezero-pressure balloon of the present invention to the safety catheter1600 of the present invention, which can be used with or without theslit valves, is described with respect to FIGS. 12 and 16 and includes,in Step 1210, assembling a first proximal leg 1620 of the balloon 1610over the distal end of the drainage catheter shaft 1630 in an “inverted”direction (open end toward the balloon interior as shown in FIG. 16).This inverted connection is accomplished with a mechanical release thatcan be formed, for example, merely by using the shape of the proximalleg 1620 of the balloon 1610 or by using a separate compression device,such as an elastic band, or by using adhesives that removably connectthe proximal leg 1620 to the drainage catheter shaft 1630. In acompression only example, the proximal balloon seal is, thereby, formedby the force of the “inverted” relatively non-compliant proximal leg1620 being extended over and around the distal end of the flexibledrainage catheter shaft 1630 by, for example, stretching the siliconematerial of the drainage catheter shaft 1630 to reduce its outerdiameter. The other, distal leg 1640 of the balloon 1610 can, then, beattached in Step 1220 using cements (as in the first example above).

To further aid in balloon assembly and catheter deflation and insertion,the outer diameter of the catheter 1600 under the balloon 1610, as wellas the inner diameter of the distal balloon leg 1640, can be reduced ascompared with the outer diameter of the drainage catheter shaft 1630,which configuration is shown in FIGS. 16 to 19. The reduced-diameterportion of the catheter 1000 is referred herein as the distal tipportion 1650 and extends from the distal end of the drainage cathetershaft 1630 at least to the distal end of the distal balloon leg 1640. Asshown, the distal tip 5 also can have the same reduced diameter (or canbe reduced further or increased larger as desired). Thus, if the outerdiameter of the distal tip portion 1650 is reduced immediately distal ofthe proximal balloon seal 1620, any predetermined pull force willstretch the catheter shaft 1630, thereby reducing the outer diameter ofthe catheter shaft 1630 at the proximal balloon seal and allowing theproximal balloon leg 1620 to slide or peel distally and deflate theballoon quickly, at which time all fluid is released therefrom into thebladder or urethra, for example. It is envisioned that the proximalballoon leg 1620 can be mounted with the balloon leg 1620 in anon-inverted or “straight” position if desired with similar results.However, in such a configuration, sliding of the proximal leg 1620 overthe distal end of the catheter shaft 1630 may be more resistant to apulling force on the exposed proximal end of the catheter shaft 1630.

With a zero-pressure configuration as described and referred to herein,the balloon 1010 is under zero-pressure or low pressure. Thus, theinflation device (e.g., a syringe) need not be configured to deliverpressure much above the low pressure range described above. Merepresence of the filling liquid in the balloon, makes the balloon largeenough to resist and prevent movement of the balloon into the urethraand out of the bladder without having an internal, high pressure. Assuch, when inserted improperly in the urethra, the balloon will simplynot inflate because there is no physical space for the balloon to expandand because the inflation pressure remains beneath the urethral damagingpressure threshold. If the inflation device is configured for lowpressure, even maximum delivered pressure to the balloon will beinsufficient to inflate the balloon within the urethra, therebypreventing any possibility of balloon inflation inside the urethra.

In the other case where the balloon is inflated properly within thebladder but the catheter is improperly removed out from the patientwithout deflating the balloon, safety devices of the invention preventtearing of the urethra upon exit. Any combination of the internalballoon valve 1012 (e.g., the slit valve of FIG. 13 formed through thewall of a portion of the drainage lumen 1120 located inside the balloon1010) and the removable proximal balloon seal 1620 can be used; one orboth can be employed to provide the safety features of the invention. Inoperation, when a predetermined inflation pressure is reached, theinternal balloon valve 1012 opens and any fluid in the balloon 1010 isemptied through the drainage lumen 1120 into the bladder (distal) and/orthe external drain bag (proximal), the latter of which is notillustrated. As set forth above, the point at which pressure causes theinternal balloon valve 1012 to open is defined to be less than thepressure needed to damage the urethra when a fully inflated prior-artballoon catheter is improperly removed as described herein. In alow-pressure state, in which the balloon 1010 is filled with a fluid(either liquid or gas), there is not enough pressure to force open theinternal balloon valve 1012 and permit exit of the fluid out from theballoon 1010. In a higher-pressure state (below urethra damagepressure), in contrast, pressure exerted on the fluid is sufficient toopen the internal balloon valve 1012, thus permitting the fluid toquickly drain out of the balloon 1010 and into the drainage lumen 1120.

In a situation where the balloon 1010 is in the urethra and inflation isattempted, pressure exerted by the surrounding urethral wall on theinflating balloon 1010 will cause the internal balloon valve 1012 toopen up well before the balloon 1010 could inflate. Thus, the ballooninflation fluid will, instead of filling the balloon 1010, exit directlyinto the drainage lumen 1120. In an alternative embodiment, the fluidused can be colored to contrast with urine (or any other fluid that isenvisioned to pass through the drainage lumen). Thus, if the balloon1010 is inserted only into the urethra and inflation is attempted, theinflating fluid will immediately exit into the drainage lumen and enterthe exterior (non-illustrated) drain bag. Thus, within a few seconds,the technician will know if the balloon 1010 did not enter the bladderand inflate there properly. In such a situation, the technician needs toonly insert the catheter further into the urethra and attempt inflationagain. The absence of further colored inflation fluid in the drain bagindicates that correct balloon inflation occurred.

In the other situation where the balloon 1010 is inflated within thebladder and the catheter 100 is pulled out from the bladder withoutdeflating the balloon 1010, pressure exerted by the urethrovesicaljunction 11 upon the inflated balloon 1010 will cause the valve 1012 toopen up quickly and cause fluid flow into the drainage lumen 1120 beforeinjury occurs to the junction 11 or the urethra. If, in such asituation, the catheter is also equipped with the removable proximalballoon end, then, as the removable proximal balloon end is peeling offof the proximal side, the slit valve opens up to relieve pressure eitherbefore or at the same time the peeling off occurs. This allows theinflation fluid to exit even faster than if just the valve 1012 ispresent.

Exemplary embodiments of the internal balloon valve 1012 are illustratedin FIGS. 14 and 15. This internal balloon valve 1012 is formed bycutting the wall of the drainage lumen 1120 at the portion of thecatheter within the balloon 1010. The slit can be a single cut or aplurality of cuts. Some exemplary slit valves other than those shown aredescribed in U.S. Pat. No. 4,995,863 to Nichols et al., all of which canbe utilized for the present invention. The slit-opening-pressure,therefore, can be regulated by adjusting the number, length and spacingof the slit(s) and the thickness of the drainage lumen wall 1122. Forexample, the length and orientation of the slit(s) 1012 determines thepressure at which it/they will open and drain the balloon inflationlumen 1130. In one particular embodiment shown in FIG. 15, the slits1124 are cut through the elastomeric walls in a way that results in awedge-shaped cross-section. With this wedge shape, fluid within theballoon can drain under pressure easily. The wedge can be increasing ordecreasing. With the former, the edges are chamfered towards one anotherfrom the central axis of the balloon toward the exterior thereof and,with the latter, the edges are chamfered towards one another from theexterior of the balloon toward the central axis.

In another exemplary embodiment, a non-illustrated, thin-walled slittedsleeve can be disposed over the portion of the drainage catheter wall1122 within the balloon 1010 and covering a throughbore fluidicallyconnecting the interior of the balloon 1010 to the interior of thedrainage lumen 1120. As such, pressure within the balloon 1010 will openthe slit(s) of the sleeve, thereby fluidically connecting the balloon1010 interior with the drainage lumen 1120 to transfer fluid in theballoon 1010 to the drainage lumen 1120. Each of these exemplary balloonconfigurations entirely prevents damage caused by improper inflation orpremature removal.

Alternatively, the balloon wall itself could be modified to burst at aparticular pressure to release the inflation media. This weakenedsection could be created by mechanical, chemical, or thermal treatmentfor example. Mechanical measures may be accomplished by scratching thesurface and, thus, thinning the balloon wall in a particular section tocause it to burst at a pre-determined pressure or actually slicing orpunching a hole in the wall and covering the area with a thinner, weakerfilm of material which will tear at a predetermined pressure lower thanthe rest of the balloon. Likewise, a chemical solvent could be appliedto create the same effect as the mechanical device above by makingchemical changes to the plastic molecular structure of the balloon walland, thereby, weakening a desired section of the balloon wall. Weakeninga section of the wall by heat to thereby re-orient its molecularstructure (much like softening by annealing) is also possible.Therefore, the preferential tearing of the balloon wall at apredetermined internal pressure can be effected in a number of ways asexemplified by, but not limited to, the methods described above.

FIGS. 16 to 18 illustrate the exemplary embodiment of the inventivecatheter 1000 with the everting removable balloon 1010. These figuresillustrate the situation where the balloon 1010 is inflated within thebladder and, as indicated by the pull arrow, the catheter 1000 is pulledout from the bladder without deflating the balloon 1010. Here, thedistal seal 1610 of the balloon 1010 is fixed to the distal tip portionof the catheter 1000, which tip 5 has a reduced outer diameter ascompared to the drainage catheter shaft 1020, and the proximal seal 1620is removably attached (e.g., with a compression seal) to the reduceddistal tip section. The pulling force causes the drainage catheter shaftto move in the proximal direction out of the urethra and, thereby,compress the proximal side of the inflated balloon 1010 against theurethrovesical junction 11. As the catheter shaft 1020 moves proximally,the force on the proximal seal 1620 increases until the seal breaks freeof the catheter shaft 1020, referred to herein as the breakaway point.FIG. 17 illustrates the now partially inflated balloon 1010 just afterthe breakaway point occurs. Because the diameter of the distal tipportion is reduced in comparison to the distal end of the catheter shaft1020, a gap opens up between the inner diameter of the proximal sealportion of the balloon 1010 and the outer diameter of the distal tipportion. This gap allows the inflating fluid to exit the balloon 1010quickly into both the urethra and the bladder before injury occurs tothe junction 11 or to the urethra. As the central portion of the balloon1010 is still larger than the urethral opening of the junction 11, thefriction and force imparted on the balloon 1010 causes the balloon 1010to roll over itself, i.e., evert, until it is entirely everted as shownin FIG. 18. At this time, all of the inflating fluid is either in theurethra and/or in the bladder.

In an exemplary embodiment of the removable proximal balloon seal 1612,a pulling force in a range of 1 to 15 pounds will cause the proximalballoon seal 1612 to pull free and allow eversion of the balloon 1010,i.e., the breakaway point. In another exemplary embodiment, the range offorce required to meet the breakaway point is between 1 and 5 pounds, inparticular, between 1.5 and 2 pounds.

The catheter 200, 300, 1000 according to the invention can be used invascular applications. It is known that every vessel has a tearingpressure. Balloons are used in coronary arteries, for example. If acoronary artery balloon were to burst, there would be less damage if theburst was controlled according to the invention. The same is true for arenal or iliac blood vessel. In such situations, the breakaway catheterimproves upon existing catheters by making them safer. From the urinarystandpoint, the breakaway balloon will not only prevent injury, but willalso be a signal to the technician that he/she needs to obtain theassistance of a physician or urologist with respect to inserting thecatheter.

1. A safety catheter, comprising: a multi-lumen shaft having: a proximalshaft portion having a distal end with given outer diameter; a distaltip portion having an outer diameter less than the given outer diameter;and a hollow balloon disposed at a junction of the proximal shaftportion and the distal tip portion, the balloon having: a distal legfixedly secured to the distal tip portion; and a proximal legtemporarily secured to the proximal shaft portion.
 2. The safetycatheter according to claim 1, wherein: the proximal leg of the hollowballoon is relatively inflexible in relation to the distal end of theproximal shaft portion; and the distal end of the proximal shaft portionand the proximal leg of the hollow balloon form a removable compressionseal therebetween.
 3. The safety catheter according to claim 2, whereinthe removable compression seal has a breakaway point at a pull force ofbetween approximately 1 pound and approximately 15 pounds applied to theproximal shaft portion.
 4. The safety catheter according to claim 1,wherein the proximal leg is temporarily secured to the proximal shaftportion in an inverted orientation.
 5. The safety catheter according toclaim 2, wherein the removable compression seal has a breakaway point ata pull force of between approximately 1 pound and approximately 5 poundsapplied to the proximal shaft portion.
 6. The safety catheter accordingto claim 2, wherein the removable compression seal has a breakaway pointat a pull force of between approximately 1.5 pounds and approximately 2pounds applied to the proximal shaft portion.
 7. The safety catheteraccording to claim 2, wherein, when the balloon portion is inflated witha fluid and a pull force of greater than approximately 15 pounds isapplied to the proximal shaft portion, the compression seal exceeds abreakaway point and thereby deflates the inflated hollow balloon.
 8. Thesafety catheter according to claim 2, wherein, when the balloon portionis inflated with a fluid and a pull force of greater than approximately5 pounds is applied to the proximal shaft portion, the compression sealexceeds a breakaway point and thereby deflates the inflated hollowballoon.
 9. The safety catheter according to claim 2, wherein, when theballoon portion is inflated with a fluid and a pull force of greaterthan approximately 2 pounds is applied to the proximal shaft portion,the compression seal exceeds a breakaway point and thereby deflates theinflated hollow balloon.
 10. The safety catheter according to claim 3,wherein the hollow balloon is operable to fold back upon itself whenremoved from the proximal shaft portion.
 11. The safety catheteraccording to claim 1, wherein the hollow balloon is operable to inflatewith and withstand pressures of between approximately 0.2 atmospheresand 0.5 atmospheres without an appreciable increase in diameter.
 12. Thesafety catheter according to claim 1, wherein: the hollow balloondefines a balloon interior; and the multi-lumen shaft has: a proximalend; a fluid drain lumen defining: a distal fluid drain opening at thedistal tip portion distally of the distal leg; and a proximal fluiddrain opening fluidically connected to the distal fluid drain opening; aballoon inflation lumen fluidly connected to the balloon interioradjacent the proximal end of the multi-lumen shaft; and an internalballoon valve operable to selectively open a channel between the fluiddrain lumen and the balloon interior.
 13. The catheter according toclaim 12, wherein the internal balloon valve is operable to open thechannel when a pressure in the balloon is between approximately 0.3atmospheres and approximately 1.5 atmospheres.
 14. A urinary safetycatheter, comprising: a multi-lumen shaft having: a length sufficient toperform urinary catheterization; a proximal shaft portion having: aproximal end; and a distal end with given outer diameter; a distal tipportion having an outer diameter less than the given outer diameter; ahollow balloon disposed at a junction of the proximal shaft portion andthe distal tip portion, the balloon defining a balloon interior andhaving: a distal leg fixedly secured to the distal tip portion; and aproximal leg temporarily secured at the distal end of the proximal shaftportion; a fluid drain lumen defining: a distal fluid drain opening atthe distal tip portion distally of the distal leg; and a proximal fluiddrain opening at the proximal shaft portion and fluidically connected tothe distal fluid drain opening; and a balloon inflation lumen fluidlyconnected to the balloon interior adjacent the proximal end of themulti-lumen shaft.